The long-term objectives of this project are to contribute to knowledge about the nature and origins of postpartum psychopathology and parenting difficulties among teenage mothers, and the transactional relationships that heighten future mental health risks for both mother and child. The specific aims are to investigate mental health problems as precursors to teenage pregnancy, risks for postpartum psychopathology and the reciprocal processes between teenage parenting, maternal psychopathology and infant dysregulated behavior and emotions. In order to develop specific expertise required as an independent investigator, this K01 proposal encompasses three training goals for the candidate: (i) to gain a fuller understanding of developmental models of psychopathology specific to teenagers; (ii) to develop skills in the assessment of teenage parenting and infant dysregulation; and (iii) to develop expertise in longitudinal statistical analyses to study developmental phenomena over time. These goals will be achieved in a prospective substudy of a longitudinal, large-scale (n=2,451) investigation of girls' behavioral and emotional development (the Pittsburgh Girls Study: PGS). At the start of the substudy data collection, the girls in the PGS will be ages 11-14 years and 6 annual waves of data will already have been collected using multiple informants. It is estimated that 239 teenagers will become mothers during the K01 award period and that a minimum of 191 will participate in the substudy. Participants will be asked to visit the research laboratory with their infant at 2-3 months and at 12 months post delivery for assessment of maternal mental health, parenting and infant behavior and filming of mother-infant interactions. Information from this project may ultimately improve children's welfare by leading to the development of early interventions to reduce mental health risks for teenage pregnancy, postpartum psychopathology and parenting difficulties among adolescents that have long-term, adverse consequences for offspring.